Serena Williams says she frequently wondered how she would keep going after returning to the practice courts following the birth of her first child.

The 23-time Grand Slam singles champion will return to the WTA Tour at Indian Wells in California this week.

The 36-year-old American said she is motivated by the thought of playing long enough for her six-month-old daughter to have memories of watching her.

However she says “It’s been hard, and there have been so many days, even still, when I’m like, ‘how am I going to keep going?’

“It’s been really, really difficult but I keep going and I know that I might not be at my best yet, but I’m getting there and every day is a new day and every day I should be getting better.

“As long as I’m moving forward, even if it’s at a turtle’s pace, then I’m OK with that.

Williams was speaking before competing at the Tiebreak Tens event at New York’s Madison Square Garden.

In an article last month, she wrote she feels “lucky to have survived” Alexis Olympia’s birth, having suffered a pulmonary embolism after an emergency Caesarean section.

For now, having played an exhibition match in Abu Dhabi in late December and a doubles rubber for the US Fed Cup team against the Netherlands last month, she says the time is right for her to return.